P0137
UniversalO2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
Medium SeverityThis code indicates that the exhaust gas oxygen (O2) sensor in Bank 1 Sensor 2 is reporting a voltage reading that is consistently too low, signaling a lean condition or an issue with the sensor's circuit. This can lead to increased fuel consumption, higher emissions, and potentially poor engine performance over time.
⚠️ Before You Begin (Safety First)
Always ensure the vehicle is safely secured on a level surface before working underneath. Disconnect the battery before performing any electrical work. Allow the exhaust system to cool completely to avoid severe burns, as O2 sensors are located in hot areas.
Common Symptoms
- Check Engine Light illumination
- Reduced fuel economy
- Engine hesitation or misfires
- Rough idle
- Failed emissions test
Common Causes
- Faulty oxygen sensor (Bank 1 Sensor 2)
- Wiring harness issues (frayed, corroded, or shorted wires)
- Exhaust leak near the sensor
- Contaminated sensor (e.g., by silicone sealant, oil, or coolant)
- Faulty Engine Control Module (ECM), though less common
Frequently reported on: Honda Civic (2001-2005), Toyota Camry (2002-2006), Ford F-150 (2004-2008), Chevrolet Silverado (2003-2007), Subaru Forester (2000-2005)
Diagnostic Steps
- Verify the code with an OBD-II scanner and note any other codes present.
- Inspect the wiring and connector for Bank 1 Sensor 2 for any visible damage, corrosion, or loose connections.
- Check for exhaust leaks near the affected O2 sensor, as this can cause incorrect readings.
- If no visible issues are found, consider replacing the Bank 1 Sensor 2 oxygen sensor. Ensure the engine is cool before attempting removal.
- Clear the P0137 code and drive the vehicle to see if the code returns.
👨🔧 When to Call a Professional
If after basic diagnostics (checking wiring, clearing the code) the problem persists, or if you lack the necessary tools or comfort working with exhaust components, it is best to consult a certified mechanic to accurately diagnose and resolve the issue.
Commonly Asked Questions
What does "Bank 1 Sensor 2" mean?
Bank 1 refers to the side of the engine that contains cylinder #1. Sensor 2 refers to the oxygen sensor located after the catalytic converter (downstream sensor), which monitors the converter's efficiency.
Can I drive with a P0137 code?
While often not critical for immediate driving, it's not recommended for long periods. It can lead to decreased fuel economy, increased emissions, and potential damage to the catalytic converter over time.
Is it possible for an exhaust leak to cause P0137?
Yes, an exhaust leak near the sensor can draw in outside air, causing the sensor to incorrectly read a lean condition (low voltage) and trigger the P0137 code.
Should I replace both O2 sensors if I get P0137?
Generally, only the faulty sensor (Bank 1 Sensor 2 in this case) needs to be replaced. However, if the other sensors are original and high mileage, you might consider replacing them for preventative maintenance.
How do I test the O2 sensor's circuit?
You can use a multimeter to check for proper voltage (typically 0.1-0.9V for a zirconium sensor, or 2.5V reference for wideband sensors) and resistance (for the heater circuit) directly at the sensor's connector or the ECM connector. This often requires a wiring diagram and specific diagnostic tools.